1. Field of Invention
The invention relates to an insulating paper piece for electric motors, for improving electrical insulation in those portions of an electric motor of a distributed winding structure where single pole coils are disposed adjacently, and an electric motor making use of the same to improve electrical insulation.
2. Description of Related Art
Electric motors of a distributed winding structure are included as a type of electric motor. They are structured so that when a plurality of single pole coils belonging to a group of coils of a plurality of phases are arranged on a stator core, a part of the coil ends projecting from both end surfaces of the stator core are arranged such that the ends of the coils of one phase and ends of the coils of another phase overlap one another.
Here, a single pole coil means one unit coil constituted by winding an electric wire a plurality of times in a manner to form one loop. Groups of coils of different phases can each be constituted by electrically connecting a plurality of such single pole coils to one another. Hereinbelow, a “single pole coil” referred to in the specification of the application has the same meaning as described above.
Such electric motors, of a distributed winding structure, need to have electrical insulation between insert portions of the respective single pole coils to be inserted in slots of a stator core and the stator core, and also need to have electrical insulation between coil end portions which have different phases, that is, phase insulation.
Conventionally, for example, as found in JP-A-11-266557, electrical insulation between a single pole coil 8 and a stator core 5 is achieved by mounting slot insulation paper pieces 91 (FIG. 15), which are bent to have a substantially U-shaped cross section so as to extend along inner wall surfaces 51 of the slots 50 as shown in FIGS. 15 and 16.
Also, provided on the slot insulation paper piece 91 are cuff portions 915, which protrude from the slots 50 to be folded toward an end surface of the stator core 5, to ensure a spacing between the coil ends 82 and the end surface of the stator core 5, that is, a so-called creeping distance. As noted, JP-A-11-266557 shows a conventional slot insulation paper piece.
Also, as shown in FIGS. 17 and 18, phase insulation is achieved by interposing strips of phase insulation paper 92 (FIG. 17) between U-phase and V-phase and between V-phase and W-phase, in the case where, for example, respective coil ends 82 of a single pole coil 8 (U) of U-phase, a single pole coil 8 (V) of V-phase, and a single pole coil 8 (W) of W-phase partially overlap one another. In addition, JP-A-5-292693 proposes a structure in which a pair of phase insulation paper 92 pieces disposed on both surfaces of a stator core are connected to each other by means of bands or strips between edges of each insulation paper 92 of the pair.